Heat exchanger units in which the synthesis gas radiant cooler is installed vertically and the synthesis gas convection cooler, the crude gas-clean gas heat exchanger as well as the crude gas-nitrogen heat exchanger are installed horizontally have been known. Even though this arrangement offers the advantage of a small overall height of the equipment installed, it entails the decisive drawback that there is a risk of encrustation and clogging of the horizontal heat exchanger tubes and of the connection lines by the flue dust and slag particles carried by the synthesis gas.
Residual dust remains as a dust deposit in the heat exchanger tubes after the unit has been switched off, because there is no self-cleaning due to the force of gravity of the horizontal tubes. If moisture enters the system during the stopping and/or during the heat-up or start-up period, the residual dust may solidify and bake on the heat exchanger tubes. This is the source of complete clogging of the tubes during the subsequent operation. The units with clogged tubes are no longer able to function, and the consequence of this is the shutdown of the entire unit, loss of production, and later expensive cleaning of the heat exchanger tubes and of the connection lines.